Method of honing a gear



Dec. 27, 1966 K. J. DAVIS 3,293,805

METHOD OF HONING A GEAR Filed Dec. '24, 1965 INVENTOR.

KENNETH J. DAVIS AT RNEYS United States Patent ()fiice 3,293,805 Patented Dec. 27, 1966 3,293,805 METHOD OF HONING A GEAR Kenneth J. Davis, Grosse Pointe, Mich., assignor to National Broach & Machine Company, Detroit, Mic-11., a corporation of Michigan Filed Dec. 24, 1963, Ser. No. 333,065 2 Claims. (Cl. 51287) The present invention relates to a method of honing a gear and is a continuation-in-part application of my copending application, Serial No. 227,290, filed October 1, 1962, now Patent No. 3,177,623, dated April 13, 1965, which in turn is a continuation-in-part application of my copending application, Serial No. 769,440, filed October 24, 1958, now Patent No. 3,088,251, dated May 7, 1963.

In gear finishing, and particularly in gear honing, it is desirable to maintain a pressure contact between the working surfaces of the teeth of the tool and the teeth of the work gear, with the axes of the tool and work gear being preferably crossed as is well known in the art. However, it is also desirable to permit a limited yielding between the tool and work gear so that excessive stresses will not be transmitted to the teeth of the tool. In the case of honing such stresses may cause the hone to break down rapidly or it may even cause the teeth of the hone to break out of the tool.

The present invention was developed primarily for permitting a gear honing operation to (1) allow for substantial eccentricity in a work gear without injury to the honing tool and (2) to automatically correct such eccentricity. If a work gear when initially meshed with the honing tool had substantial eccentricity and was brought into mesh with its low side in firm engagement with the honing tool, the first half revolution of the work gear would subject the honing tool to destructive pressures.

The present invention utilizes a resilient, yieldable, annular support or coupling ring between the honing tool and its support under initial substantial compression as will be explained in detail later on in the specification. The average operating pressure between the teeth of the honing tool and work gear may be controlled while at the same time some yielding or displacement of the honing tool relative to its support and to the work is permitted. The resilient ring is very sensitive to the tool displacement, which may be only a few thousandths of an inch. This displacement of the tool results in additional compression of the resilient ring, which may be made from rubber or other yieldable material, and hence results in an increase in pressure whenever a displacement of the tool takes place.

In addition, the use of the resilient mounting or ring in a gear honing machine gives rise to the second function outlined above; namely, correction of the eccentricity of a work gear. This, of course, is because the radial pressure acting between the work gear and hone is a function of the yieldable force exerted on the hone by the resilient mounting. Thus, when due to eccentricity the hone is forced or displaced further away from the work, the rubber or other resilient material is subjected to more distortion and hence exerts a larger restoring force on the hone. Thus, the abrading action of the hone is variable in substantial amounts in accordance with the relatively minute displacement of the hone thereby if eccentricity is present, which results in the application of greater honing effort on relatively high portions of the work gear.

The material of the annular ring interposed between the tool and its support has been described as a yieldable resilient material such as rubber. A resin compound is used in the production of the annular toothed peripheral portion of the honing tool and is slightly yieldable and highly resilient. From the foregoing it will of course be apparent that the nature of these two materials is essentially dissimilar. portion of the honing tool is quite hard and maintains a form except when displaced under relatively high unit pressure. When this occurs, the resilience of the material causes it to regain its initial form as soon as the high unit pressure has been removed.

On the other hand, the annular coupling ring which connects the tool support and the annular toothed peripheral portion of the tool is relatively soft and is intended to yield so as to limit the total force acting between the work gear and the gear-like honing tool to a few pounds, as for example between one and fifty pounds. Similarly, when the work gear and honing tool are in loose mesh, the annular coupling ring limits the total circumferential force acting between the gear and tool to a correspondingly small range. Thus, the function of the yieldable coupling ring is to establish and maintain a relatively small average force acting between the gear and tool. This force is, of course, variable in accordance with displacement as previously described.

It is an object of the present invention to provide a method of honing a gear which comprises the steps of mounting a work gear for rotation in mesh at crossed axes with a rotary gear-like honing tool having at least its tooth portion formed of an abrasive material, driving the gear or tool in rotation and thereby driving the other through the meshed engagement therebetween, and maintaining the gear and tool in radially acting pressure contact with each other at a pressure which varies directly in accordance with the radial spacing therebetween.

Another object of the present invention is to provide a method of the aforementioned type wherein the gear and tool are maintained in radially acting pressure contact with each other at a pressure of between 1 and 50 pounds which varies directly in accordance with the radial spacing therebetween.

It is thus another object of this invention to provide a method of the aforementioned type having certain advantages contributing to efliciency and reliability.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawing illustrating preferred embodiments of the invention, wherein:

FIGURE 1 is an elevational view of a gear honing machine.

FIGURE 1A is a fragmentary elevational view illustrating the relationship between a gear and tool with their axes crossed.

FIGURE 2 is an elevational view of a honing tool and tool support.

FIGURE 3 is a fragmentary enlarged sectional view of the honing tool illustrated in FIGURE 2.

FIGURE 4 is a fragmentary sectional view similar to FIGURE 3 of a modified honing tool.

FIGURE 5 is a diagrammatic view of a modification of the gear honing machine illustrated in FIGURE 1.

As mentioned previously, the present invention relates to a recent development known as gear honing in which a gear-like tool, preferably after heat treatment or other hardening operation, is run in mesh with a gear-like hone. A hone is a tool in the form of a gear having at least its toothed portions formed of a relatively hard but slightly yieldable and highly resilient resin having abrasive particles separately embedded therein.

The operation is carried out by driving either the gear or the bone in rotation thereby driving the other of the members which is mounted for substantially free rota- The material of the peripheral toothed I tion. During meshed rotation between the gear and hone a relative traverse is carried out in a plane parallel to the axes of both spindles or supports to insure distribution of the finishing action of the hone from end to end of the gear teeth. This relative traverse is normally in a direction parallel to the axis of the gear.

To insure the pressure contact between the teeth of the gear and hone necessary to produce a gear finishing operation, one of the supports is mounted for movement toward and away from the other support, and means are provided for applying a force to move the said one support so as to establish an initial predetermined pressure contact between the teeth of the gear and hone. In addition, according to the present invention, a yieldable resilient support ring is provided which automatically compensates for any eccentricity in the work gear.

Referring now to FIGURE 1, there is shown a machine which embodies the principle of the present invention and which is designated by the numeral 10. Described in general terms, the machine comprises a frame indicated generally at 12 including a base 14, a column 16, and a forwardly projecting overhanging portion 18. A vertically movable knee is carried by the frame 12 and at its top is provided with a slide or carriage 22.

The knee 20 is vertically movable to accommodate gears of diiferent sizes and to provide a preliminary setting of the machine. Suitable means such, for example, as a vertically extending feed screw 24 is provided for effecting vertical adjustment of the knee 20, this being accomplished by rotation of the feed screw 24 and a nut (not shown) as controlled by a manually operable handle, not shown, applied to the square end of an actuating shaft 26. The carriage 22 is mounted on suitable ways 28 provided at the top of the knee 20 and may be mounted thereon for reciprocation in a horizontal plane in a direction perpendicular to the plane of FIGURE 1. In other cases, as is well understood in the art, the direction of traverse in the horizontal plane may be varied.

Mounted on the carriage 22 is a rotary work support means including a headstock (not shown) and a tailstock indicated at 30. In the gear honing operation the gear G is in mesh with a honing tool T. While the axes of the gear G and honing tool T in FIGURE 1 are indicated as parallel, in practice the axes of these members will be crossed in space normally at an angle of between three and thirty degrees. The tool T is carried by an angularly adjustable head 32, the head 32 being mounted for adjustment about a vertical axis to vary the crossed axes setting between the gear G and tool T. A motor 34 is provided and is connected to the spindle 36 of the tool T by gearing indicated at 38 to effect positive rotation of the tool T and hence to drive the gear G through the meshed engagement of the parts. Normally, suitable traverse means such as the screw 40 and nut 42 are provided for effecting relative traverse between the carriage 22 and the knee 20. This relative traverse is in a direction occupying a horizontal plane, and hence is in a plane parallel to the axes of both the gear G and tool T.

In FIGURE 1 the tool head 32 is shown adjusted into a position in which the axis of the tool T is parallel to the axis of the work gear G. This is merely to simplify the illustration and in practice the gear and tool are operated at crossed axes as indicated in FIGURE 1A. In this figure the upper portion of the gear G is illustrated with its axis parallel to the plane of the paper and in mesh with a gear-like tool T which as is apparent from the figure, has its axis extending at an angle to the plane of the figure. The relationship illustrated in FIGURE 1A is, of course, brought about by adjusting the head 32 angularly about a vertical axis. It will, of course, also be recognized that the relationship illustrated in FIG- URE 1A requires that the gear and tool have helix angles which differ to provide for conjugate meshing of the gear and tool with their axes crossed. For example,

with the axes crossed at an angle of 15 degrees a spur work gear would require a tool having a 15 degrees helix angle.

In order to carry out the honing operation under sufiicient pressure contact to remove material from the surface of the hardened teeth of the gear G the knee 20 is moved upwardly to bring the teeth of the gear G into mesh with the teeth of the tool T under an initial predetermined pressure as will be explained in more detail later on in the specification.

Referring to FIGURE 2, there is shown the tool T mounted on the support 36 and comprising an inner support body 50 of circular cross-section, the support body 50 having a centrally located hole 52 by means of which it may be mounted on the tool support 36. Located concentrically with the support body 50 and spaced radially outwardly therefrom is an annular toothed body 54, the peripheral portions of which are provided with teeth 56 which may be conjugate to the teeth of the gear G to be finished. The annular toothed body 54 is separated radially from the outer peripheral portion of the support body 50 and this space is filled with an annular coupling ring 58 formed of a yieldable material such for example as a natural or synthetic rubber, or a suitable yieldable plastic. The ring 58 is highly resilient and supports the toothed annular body 54 on the support body 50. Due to its yieldability radial displacement of the annular toothed body 54 relative to the support body 50 and tool support 36 is permitted.

As mentioned previously, the present invention may be used in conjunction with gear shaving or gear lapping, its maximum utility is obtained when the annular toothed body 54 is formed. of an abrasive material providing a gear hone T. A material which has proven exceptionally etficient in producing gear homes is a resin compound formed of equal parts by weight of epoxy resin and a relatively fine abrasive material such for example as powdered silicon carbide. The epoxy resin is the result of a reaction between epichlorohydrin and Bisphenol-A carried out in the presence of a water solution of sodium hydroxide at a temperature of approximately degrees Fahrenheit. The reaction is continued to produce an epoxy resin having an approximate molecular weight of' 400. The epoxy resin is liquid. The epoxy value, equiv. /100 gm. is 0.50. The hydroxyl groups per molecule are 0.14-0.28.

This resin compound, in order to produce the gear honing tools having the toothed peripheral portion shown, is mixed with abrasive material and hardener in approximately the following proportions by weight:

Resin compound 100 Abrasive grains (46-280 grit) 100-150 Hardener (aliphatic or polyamine such as metaphenylene diamine) 15-20 This material may readily cast to the solid form and is characterized in part by its dimensional stability which permits casting to the final required dimensions.

Referring now to FIGURE 3, there is shown a support body 60 having a hub 62 and radially extending flanges 64. An intermediate annular support body 66 is illustrated herein as fastened to the support body 60 by screws 68. The annular toothed gear finishing or honing portion of the tool T is illustrated at 70 and includes gear-like teeth 72 and a continuous annular body portion 74. Intermediate the annular body 74 and the support body 66 is a yieldable support ring 76 which may be formed of natural rubber, synthetic rubber, or a suitable plastic material. The parts may be assembled in the relationship shown in FIGURE 3 by maintaining the rubber or other suitable material under substantial compression while the annular body 74 is assembled to surround it and thereafter releasing the rubber.

It will, of course, be appreciated that the yieldable support ring 76 permits limited radial circumferential and 'tween one and fifty pounds.

axial displacement between the bodies 66 and 74. The amount of resistance which the support ring 76 opposes to displacement of the annular body 74 on the support body 66 may be controlled as desired. A primary control is in the compounding of the material of the support ring 76. The radial dimension or thickness of the ring is, of course, also effective to influence its supporting action. In FIGURE 4, the honing tool is identical to the tool shown in FIGURE 3 with the exception that a relatively radially thin yieldable support ring 82 is provided between the support body 84 and the toothed portion 86 rather than the relatively thick ring 76 used in FIGURE 3. Finally, the degree of initial compression of the annular support ring enters into its effectiveness as a support.

In gear finishing, and particularly in gear honing, it is desirable to maintain a pressure contact between the working surfaces of the teeth of the tool T and the teeth of the gear G. However, it is also desirable to permit a limited yielding so that excessive stresses will not be transmitted to the teeth of the tool T. In the case of honing such stresses may cause the hone to break down rapidly or it may even cause the teeth of the hone to break out of the tool T. By employing a yieldable support ring such as the ring 76, the average operating presure between the teeth of the tool and gear may be controlled while at the same time some yielding of the tool T relative to the work gear G is permitted. This yielding results in additional compression of the rubber or other yieldable material and hence results in an increase in pressure whenever a displacement of the toothed portion of the tool T takes place.

This is an important feature of the present invention. Consider for example the situation which may exist when the gear G and tool T are brought into mesh with initial contact at the low side of an eccentric work gear G. During rotation, as the high side of the gear G meshes with the teeth of the tool T, the tool T is displaced away from the gear, thus preventing injury or breakage of the tool T. However, this displacement of the tool T results in an increased pressure proportional to the amount of displacement so that the metal removing action of the tool T is thus in turn proportional to the displacement. Since this displacement is the result of an error which is to be corrected, the tool T automatically provides its greatest corrective action at the portions of the work gear exhibiting the greatest error, or in other words, the portions of the work gear G which require the greatest finishing action. The resilient ring 76 is very sensitive to displacement of a magnitude of only a few thousands of an inch.

As mentioned previously, material of the yieldable ring interposed between the central core and the relatively rigid annular toothed portion has been described as a yieldable resilient material. The resin compound used in the production 'of the annular toothed peripheral portion of the tool has also been described as slightly yieldable and highly resilient. From the foregoing it will, of course, be apparent that the nature of these two materials is essentially dissimilar. The material of the peripheral toothed portion of the tool is quite hard and maintains a form except when displaced under relatively high unit pressure. When this occurs, the resilience of the material causes it to regain its initial form as soon as the high unit pressure has been removed.

On the other hand, the annular coupling ring which connects the central core and the annular toothed peripheral portion is relatively soft and is intended to yield so as to limit the total force acting between the gear and the gear-like tool to a few pounds, as for example be- Similarly, when the gear and the gear-like tool is in loose mesh, the annular coupling ring limits the total circumferential force acting between the gear and tool to a correspondingly small range. Thus, the function of the yieldable coupling ring 6. is to establish and maintain a relatively small average force acting between the gear and tool. This force is, of course, variable in accordance with displacement which may be only a few thousandths of an inch as previously described.

It is desired to emphasize the fact that the total force acting between the gear and tool is quite a different matter from the unit pressure between the toothed surfaces of the gear and tool. It will be appreciated that when a high spot of limited area is present on a tooth of the gear, it may exert an extremely high unit pressure on corresponding portions of the mating teeth of the tool as it moves in mesh therethrough. This, however, will in most cases not substantially influence the total radial or circumferential force acting between the tool and gear as a whole.

By way of a specific example, a yieldable coupling ring of approximately one inch thickness and having a radial dimension of approximately one-half inoh may be formed of a good grade of rubber, either natural or synthetic, having a Shore durometer of 4080.

It should be understood from the foregoing description that when the present invention is utilized in a honing operation, the work gear G is moved vertically on the slide 22 by means of the feed screw 24 so that the gear G is brought into mesh with the tool T under a predetermined pressure contact. Later on the tool T and gear G are driven in mesh as described previously. As the teeth of the hone wear, the knee 20 is moved vertically upwardly to maintain the predetermined pressure contact.

FIGURE 5 is a diagrammatic view of a modification of the present invention wherein the gear honing machine comprises a base 84, a movable tool carriage 86 and pressure control feed mechanism 88 including a movable slide 90. The tool carriage 86 is provided with a rotary tool support 92 on which is mounted the honing tool T. The honing machine includes means for supporting a rotary work support 94 on which is mounted the work gear G. The direction of movement of the carriage 86 is directly toward and away from the axis of the work gear G, preferably with the axes of the tool T and gear G crossed. The carriage 86 has projecting rearwardly therefrom a headed bar 96 which is operatively connected to the pressure control feed mechanism 88. The pressure control feed mechanism 88 derives its actuating force from weights 98 which are carried at the upper end of a substantially vertically movable rod 100. The rod 100 is provided adjacent its lower end with an inclined abutment surface 102 which is movable in the inclined track 104 provided in the outer side of the slide 90. As an example, the slide 90 and carriage 86 may be mounted on rollers 103 and 105 respectively.

Connected to the inner side of the slide 90 is a leaf spring 104, the lower portion of which is connected by a plurality of bolts 108 to the slide 90. With such a construction the ileaf spring 104 may be adjusted vertically as will subsequently appear. It will be apparent that the leaf spring 104 is adapted to transmit forces to the stud or bar 96 tending to move the bar 96, carriage 86 and tool T to the right as viewed in FIGURE 5 and correspondingly is adapted to yield under excessive forces tending to move the carriage 86 and tool T to the left. As illustrated, the head of the bar 96 engages the extreme free end of the leaf spring 104 and hence the leaf spring 104 will yield under a minimum force for which the spring 104 is designed. It will be appreciated that if the leaf spring 104 is bodily adjusted upwardly the force under which it will yield increases and upward adjustment may be continued to a point where a solid portion of the leaf spring 104 underlies or abuts the head of the bar 96.

The rod 100 is supported in a bushing 110 which determines the frictional resistance to vertical movement of the rod 100. It will be appreciated that when the weights 93 move the rod 100 downwardly, a component of force urges the slide 90 to the right so as to maintain the tool T and gear G in a predetermined pressure relationship. The use of the gravity operated rod 100 provides irreversible means for applying a continuous feeding force of a predetermined value to the hone T. The carriage 86 may be locked against further movement during the honing operation. However, if this locking means is not applied the hone T is adapted to follow up as material is removed from the work gear G.

It should be appreciated that if eccentricity exists in the work gear G, the creation of dangerously high pressures between the gear G and the hone T is avoided by use of a leaf spring 104 which will yield so as to limit to safe values the forces developed between the teeth of the gear G and hone T.

By way of example, a series of weights 98 totalling about 30 pounds, may be effective to produce a radial force acting between the gear G and tool T on the order of 50-100 pounds. This is true even though the inclination of the abutment surface 102 is extremely high, since the frictional resistance to downward sliding movement of the rod 100 in the guide 110 exerts a controlling influence. This force is increased if an eccentric gear ca-uses carriage 86 to move to the left, since the cam mechanism is irreversible. In this case, spring 104 yields and the increase in force is determined by the amount of carriage movement and the strength and adjustment of the spring 104. This increase in lhoning pressure tends to correct the eccentricity of the gear G.

The drawings and the foregoing specification constitute a description of the improved method of honing a gear in such full, clear, concise, and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

1. The method of honing a gear with correction of eccentricity which comprises mounting a work gear member for rotation in tight mesh at crossed axes with 'a rotary gear-like tool member having at least its tooth portion formed of an abrasive material, driving one of the members in rotation and thereby driving the other member in rotation through the meshed engagement between said members, relatively traversing said members in a direction occupying a plane parallel to the axes of both of said members, establishing a substantially constant predetermined minimum force acting substantially radially between said members to establish a predetermined minimum pressure contact between the teeth of said members and applying an additional eccentricitycorrecting force acting between said members variably in accordance with variations in the center distance between the work gear member and the toothed portion of the tool member of a few one-thousandths of an inch occasioned by eccentricity of the work gear of corresponding amount of a magnitude suflicient to provide an increased stock removal effective to produce a useful correction in eccentricity of the work gear.

2. The method as defined in claim 1 which comprises applying the additional force variably in accordance with variations in the center distance between said members.

References Cited by the Examiner UNITED STATES PATENTS 162,010 4/1875 Bannister 5l168 2,245,654 6/1941 Drader et a1. 51287 X 2,913,858 11/1959 Praeg et a1 51206 3,088,251 5/1963 Davis 51206 X 3,177,623 4/1965 Davis 51105 FOREIGN PATENTS 392,385 4/1933 Great Britain.

LESTER M. SWINGLE, Primary Examiner. 

1. THE METHOD OF HONING A GEAR WITH CORRECTION OF ECCENTRICITY WHICH COMPRISES MOUNTING A WORK GEAR MEMBER FOR ROTATION IN TIGHT MESH AT CROSSED AXES WITH A ROTARY GEAR-LIKE TOOL MEMBER HAVING AT LEAST ITS TOOTH PORTION FORMED OF AN ABRASIVE MATERIAL, DRIVING ONE OF THE MEMBERS IN ROTATION AND THEREBY DRIVING THE OTHER MEMBER IN ROTATION THROUGH THE MESHED ENGAGEMENT BETWEEN SAID MEMBERS, RELATIVELY TRAVERSING SAID MEMBERS IN A DIRECTION OCCUPYING A PLANE PARALLEL TO THE AXES OF BOTH OF SAID MEMBERS, ESTABLISHING A SUBSTANTIALLY STANT PREDETERMINED MINIMUM FORCE ACTING SUBSTANTIALLY RADIALLY BETWEEN SAID MEMBERS TO ESTABLISH A PREDETERMINED MINIMUM PRESSURE CONTACT BETWEEN THE TEETH OF SAID MEMBERS AND APPLYING AN ADDITIONAL ECCENTRICITYCORRECTING FORCE ACTING BETWEEN SAID MEMBERS VARIABLY IN ACCORDANCE WITH VARIATIONS IN THE CENTER DISTANCE BETWEEN THE WORK GEAR MEMBER AND THE TOOTHED PORTION OF THE TOOL MEMBER OF A FEW ONE-THOUSANDTHS OF AN INCH OCCASIONED BY ECCENTRICITY OF THE WORK GEAR OF CORRESPONDING AMOUNT OF A MAGNITUDE SUFFICIENT TO PROVIDE AN INCREASED STROCK REMOVAL EFFECTIVE TO PRODUCE A USEFUL CORRECTION IN ECCENTRICITY OF THE WORK GEAR. 